A liquid crystal display (LCD) is a display using liquid crystal as a material. Under the action of an electric field, the arrangement of liquid crystal molecules will change, so as to affect the change of rays passing through the same, and the change of the rays can be represented by change in brightness under the action of a polaroid. In this way, the change of brightness of the rays can be controlled by controlling the electric field so as to achieve the purpose of displaying an image. At present, the liquid crystal display has been widely applied in application fields such as mobile phones, tablet computers, vehicle-mounted displays, projection TVs, etc. Among them, most liquid crystal displays and liquid crystal TVs are driven by TFT's (Thin Film Transistors), and this kind of liquid crystal displays can be generally called TFT-LCDs.
Specifically, a TFT-LCD is a non-self-luminous display, and a corresponding backlight module needs to be added to provide a corresponding planar light source. The backlight module is one of the key components of a liquid crystal display panel, and in general, backlight modules may be categorized into two types, that is, front light type and back light type. Specifically, back light type backlight modules may be categorized into side type, direct type and other types according to different positions of the backlight sources. Specifically, a side type backlight module is taken as an example, the side type backlight module may mainly include a light emitting diode (LED) light source, a light guide plate, a reflector plate, a diffuser plate, at least two mutually vertical light-collecting prism sheets, etc. The prism sheet may be generally called as BEF (Brightness Enhancement Film), and is used for limiting the visual angle of the liquid crystal display, so that most rays are emitted within the range of a front visual angle of ±(30°-60°), thereby achieving the light collection and brightness enhancement effects.
However, it is unfavorable to practical application that the visual angle of the liquid crystal display is set within a fixed range (for example, ±(30°-60°) mentioned above). This is because, in the actual use of the liquid crystal display, sometimes there may be only one person watching the display, and sometimes there may be many people watching the display at the same time, when only one person watches the display, the viewing demand of the user can be satisfied by providing enough brightness in the forward direction of the display; when many people watch the display at the same time, enough brightness needs to be provided within a large angle range of the display to meet the viewing demand of the users. At present, a solution of the problem is to provide a liquid crystal display with a large visual angle, however, this display will cause unnecessary energy consumption if there is only one user.
Therefore, a backlight module capable of regulating the visual angle of a liquid crystal display needs to be provided, in order to achieve free switch between a small visual angle and a large visual angle of the liquid crystal display.